This stage in the operation of an injection pump, referred to as "emptying", causes excess fuel to be expelled at very high pressure and at very high speed through return orifices where the fuel that is already present is at low pressure. At the interface between the jet of expelled fuel and the fuel at low pressure, this gives rise to the appearance of bubbles due to degassing which, combined with the travel speed, give rise to erosion of the walls of the return orifices by cavitation, which erosion can lead to destruction of the injection pump. One of the means for eliminating this cavitation is to increase the pressure which obtains in the return orifices of an injection pump when emptying takes place. Devices are known such as that described in document JP08296528 which teaches placing a check valve upstream from the feed to the injection pump and two rated valves downstream from the injection pump, one of the rates valves having a high rating and enabling a large flow rate and the other rated valve having a low rating for passing a low flow rate. In addition, at least one of the rated valves includes an orifice to guarantee continuous circulation of fuel. The drawback of that device is that the permanent link does not enable high and sufficient pressure to be maintained in the orifices before emptying takes place. This pressure arises only when the emptying flow appears, and that is not sufficient for avoiding orifice erosion effectively.